The goal of the proposed research is to study the functionality of the domains of the iterative type I enediyne C-1027 polyketide synthase (PKS). Conserved domains will be analysized by site-directed mutagenesis of the proposed active sites, and the mutants characterized by in vivo analysis. It is hypothesized the PKS contains an unusual acyl carrier protein (ACP) domain that requires a unique phosphopantetheinyl transferase (PPTase), which is proposed to also be a domain found within the PKS. The function of the putative ACP and PPTase domain will be analyzed by a thorough in vivo and in vitro analysis, which includes mutant generation of the proposed active sites. Finally, it is proposed that the regiochemistry of enediyne formation is controlled by the PKS. This will be tested by the creation of hybrid PKSs from C- 1027, which contains a 9-carbon enediyne core, and calicheamicin, which contains a 10-carbon enediyne core. The results will provide insights into the programming rules of enediyne biosynthesisand will allow for the generation of "unnatural" natural enediynes with predicted chemistry.